1. Field of the Invention
The present invention relates generally to a motor structure, and more particularly, to a pillow having vibration-absorbing means and heat insulating means of a motor structure.
2. Description of the Related Art
In rotation, the temperature of the stator of a common motor rises and its heat is transferred to its surroundings. The heat transferred to the bearing adversely affects its life. In a common fan motor, e.g. a fan motor disclosed in U.S. Pat. No. 5,343,104, a pillow is provided between a bearing and the stator of the motor. The heat generated in the stator of the motor transfers to the bearing through the pillow. A conventional fan motor similar to the fan motor disclosed in U.S. Pat. No. 5,343,104 will be described in the following.
FIG. 1 shows a conventional fan motor structure. It comprises an upper casing 101; a lower casing 102 having a base portion 102a and a pillow portion 102b; a bearing 103 accommodated in the pillow portion 102b; a rotation shaft 104 supported by the bearing 103; a C-ring 105 snap engaged with the rotation shaft 104 for fixing the bearing 103 at an axial location; an impeller 106; a coil unit 107, and a printed circuit board 108. The impeller 106 consists of a plurality of blades 106a, a yoke 106b, a ring-shaped magnet 106c, and a hub portion 106d. The coil unit 107 consists of an upper cover 107a, a lower cover 107b, and a stator core 107c.
When the impeller rotates, the heat generated in the coil unit 107 transfers to the bearing 103 through the pillow portion 102b and causes an adverse effect. Generally speaking, the pillow portion 102b can be made of plastic or copper.
Although the pillow portion 102b made of plastic can achieve a certain degree of insulation, most of the heat rapidly transfers to the bearing 103 through the thin sidewall of the pillow portion 102b. The pillow portion 102b made of copper can rapidly transfers heat to the bearing 103 because it can achieve a good heat conduction effect. Therefore, the pillow portion 102b cannot insulate the bearing 103 from the heat generated in the coil unit 107 to avoid the adverse effect on the bearing 103.
Moreover, when the fan motor operates, the vibration of the impeller 106 transmits to the bearing 103 through the rotation shaft 104 and then transmits to the coil unit 107 and the printed circuit board 108 through the pillow portion 102b. The slight transmission of the vibration can result in the vibration and noises of the system in which the fan motor is mounted and serious transmission of the vibration can result in the disengagement between the coil unit 107 and the printed circuit board 108 or even the disengagement of the electronic elements (not shown) from the printed circuit board 108. Therefore, if the vibration can be absorbed more effectively then the life of all the elements of the fan motor can be prolonged.